renderer: handle rendering to A8 surfaces.

I'm not sure this is 100% complete, piglit fbo-alpha now passes.

This was a guess as to why gnome-shell was broken, but I don't think
it was the correct one.

src/vrend_formats.c

@@ -261,7 +261,7 @@ static void vrend_add_formats(struct vrend_format_table *table, int num_entries)
     if (status == GL_INVALID_VALUE) {
       struct vrend_format_table *entry = NULL;
       uint8_t swizzle[4];
-      binding = VREND_BIND_SAMPLER | VREND_BIND_NEED_SWIZZLE;
+      binding = VREND_BIND_SAMPLER | VREND_BIND_RENDER | VREND_BIND_NEED_SWIZZLE;
 
       switch (table[i].format) {
       case PIPE_FORMAT_A8_UNORM:

src/vrend_renderer.c

@@ -412,6 +412,14 @@ bool vrend_is_ds_format(enum virgl_formats format)
    return vrend_format_is_ds(format);
 }
 
+static inline bool vrend_format_is_emulated_alpha(enum virgl_formats format)
+{
+   if (!vrend_state.use_core_profile)
+      return false;
+   return (format == VIRGL_FORMAT_A8_UNORM ||
+           format == VIRGL_FORMAT_A16_UNORM);
+}
+
 static inline const char *pipe_shader_to_prefix(int shader_type)
 {
    switch (shader_type) {
@@ -1508,6 +1516,7 @@ void vrend_set_framebuffer_state(struct vrend_context *ctx,
       if (status != GL_FRAMEBUFFER_COMPLETE)
          fprintf(stderr,"failed to complete framebuffer 0x%x %s\n", status, ctx->debug_name);
    }
+   ctx->sub->shader_dirty = true;
 }
 
 /*
@@ -1921,9 +1930,12 @@ static inline void vrend_fill_shader_key(struct vrend_context *ctx,
    if (vrend_state.use_core_profile == true) {
       int i;
       bool add_alpha_test = true;
+      key->cbufs_are_a8_bitmask = 0;
       for (i = 0; i < ctx->sub->nr_cbufs; i++) {
          if (!ctx->sub->surf[i])
             continue;
+         if (vrend_format_is_emulated_alpha(ctx->sub->surf[i]->format))
+            key->cbufs_are_a8_bitmask |= (1 << i);
          if (util_format_is_pure_integer(ctx->sub->surf[i]->format))
             add_alpha_test = false;
       }
@@ -2216,8 +2228,13 @@ void vrend_clear(struct vrend_context *ctx,
 
    vrend_use_program(ctx, 0);
 
-   if (buffers & PIPE_CLEAR_COLOR)
+   if (buffers & PIPE_CLEAR_COLOR) {
+      if (ctx->sub->nr_cbufs && ctx->sub->surf[0] && vrend_format_is_emulated_alpha(ctx->sub->surf[0]->format)) {
+         glClearColor(color->f[3], 0.0, 0.0, 0.0);
+      } else {
          glClearColor(color->f[0], color->f[1], color->f[2], color->f[3]);
+      }
+   }
 
    if (buffers & PIPE_CLEAR_DEPTH) {
       /* gallium clears don't respect depth mask */
@@ -2849,6 +2866,15 @@ static inline bool is_dst_blend(int blend_factor)
            blend_factor == PIPE_BLENDFACTOR_INV_DST_ALPHA);
 }
 
+static inline int conv_a8_blend(int blend_factor)
+{
+   if (blend_factor == PIPE_BLENDFACTOR_DST_ALPHA)
+      return PIPE_BLENDFACTOR_DST_COLOR;
+   if (blend_factor == PIPE_BLENDFACTOR_INV_DST_ALPHA)
+      return PIPE_BLENDFACTOR_INV_DST_COLOR;
+   return blend_factor;
+}
+
 static inline int conv_dst_blend(int blend_factor)
 {
    if (blend_factor == PIPE_BLENDFACTOR_DST_ALPHA)
@@ -2863,12 +2889,17 @@ static void vrend_patch_blend_func(struct vrend_context *ctx)
    struct pipe_blend_state *state = &ctx->sub->blend_state;
    int i;
    int rsf, rdf, asf, adf;
+   bool a8_conv = false;
    if (ctx->sub->nr_cbufs == 0)
       return;
 
    for (i = 0; i < ctx->sub->nr_cbufs; i++) {
       if (!ctx->sub->surf[i])
          continue;
+      if (vrend_format_is_emulated_alpha(ctx->sub->surf[i]->format)) {
+         a8_conv = true;
+         break;
+      }
       if (!util_format_has_alpha(ctx->sub->surf[i]->format))
          break;
    }
@@ -2880,6 +2911,13 @@ static void vrend_patch_blend_func(struct vrend_context *ctx)
       /* ARB_draw_buffers_blend is required for this */
       for (i = 0; i < PIPE_MAX_COLOR_BUFS; i++) {
          if (state->rt[i].blend_enable) {
+
+            if (a8_conv) {
+               rsf = translate_blend_factor(conv_a8_blend(state->rt[i].alpha_src_factor));
+               rdf = translate_blend_factor(conv_a8_blend(state->rt[i].alpha_dst_factor));
+               asf = translate_blend_factor(PIPE_BLENDFACTOR_ZERO);
+               adf = translate_blend_factor(PIPE_BLENDFACTOR_ZERO);
+            } else {
                if (!(is_dst_blend(state->rt[i].rgb_src_factor) ||
                      is_dst_blend(state->rt[i].rgb_dst_factor) ||
                      is_dst_blend(state->rt[i].alpha_src_factor) ||
@@ -2890,12 +2928,19 @@ static void vrend_patch_blend_func(struct vrend_context *ctx)
                rdf = translate_blend_factor(conv_dst_blend(state->rt[i].rgb_dst_factor));
                asf = translate_blend_factor(conv_dst_blend(state->rt[i].alpha_src_factor));
                adf = translate_blend_factor(conv_dst_blend(state->rt[i].alpha_dst_factor));
+            }
 
             glBlendFuncSeparateiARB(i, rsf, rdf, asf, adf);
          }
       }
    } else {
       if (state->rt[0].blend_enable) {
+         if (a8_conv) {
+            rsf = translate_blend_factor(conv_a8_blend(state->rt[i].alpha_src_factor));
+            rdf = translate_blend_factor(conv_a8_blend(state->rt[i].alpha_dst_factor));
+            asf = translate_blend_factor(PIPE_BLENDFACTOR_ZERO);
+            adf = translate_blend_factor(PIPE_BLENDFACTOR_ZERO);
+         } else {
             if (!(is_dst_blend(state->rt[0].rgb_src_factor) ||
                   is_dst_blend(state->rt[0].rgb_dst_factor) ||
                   is_dst_blend(state->rt[0].alpha_src_factor) ||
@@ -2906,6 +2951,7 @@ static void vrend_patch_blend_func(struct vrend_context *ctx)
             rdf = translate_blend_factor(conv_dst_blend(state->rt[i].rgb_dst_factor));
             asf = translate_blend_factor(conv_dst_blend(state->rt[i].alpha_src_factor));
             adf = translate_blend_factor(conv_dst_blend(state->rt[i].alpha_dst_factor));
+         }
 
          glBlendFuncSeparate(rsf, rdf, asf, adf);
       }

src/vrend_shader.c

@@ -681,6 +681,17 @@ static const char *atests[PIPE_FUNC_ALWAYS + 1] = {
    "true",
 };
 
+static int emit_a8_swizzle(struct dump_ctx *ctx)
+{
+   char buf[255];
+   char *sret;
+   snprintf(buf, 255, "fsout_c0.x = fsout_c0.w;\n");
+   sret = add_str_to_glsl_main(ctx, buf);
+   if (!sret)
+      return ENOMEM;
+   return 0;
+}
+
 static int emit_alpha_test(struct dump_ctx *ctx)
 {
    char buf[255];
@@ -1757,6 +1768,11 @@ iter_instruction(struct tgsi_iterate_context *iter,
             if (ret)
                return FALSE;
          }
+         if (ctx->key->cbufs_are_a8_bitmask) {
+            ret = emit_a8_swizzle(ctx);
+            if (ret)
+               return FALSE;
+         }
          if (ctx->key->add_alpha_test) {
             ret = emit_alpha_test(ctx);
             if (ret)

src/vrend_shader.h

@@ -63,6 +63,7 @@ struct vrend_shader_key {
    bool gs_present;
    bool flatshade;
    float alpha_ref_val;
+   uint32_t cbufs_are_a8_bitmask;
 };
 
 struct vrend_shader_cfg {